Intercellular communication is thought to play an integral role in the complex mechanisms controlling cell determination, differentiation, and morphogenesis which result in a higher organism. The proposed study will use the fruitfly, Drosophila melanogaster, to examine changes in the functional properties and biochemical composition of the cell surface through development. The sophisticated genetic methodology available for Drosophila allows the use of a powerful approach not possible in other higher eukaryotes: the systematic recognition of gene mutations that alter cell surface properties, and the analysis of the role of these genetically regulated components in developmental events. The research proposed will initially focus on changes of the cell surface properties of primordia called imaginal discs during development in both Drosophila and the closely related Dipteran, Calliphora erythrocephala. Cell surface-associated proteins and glycoproteins of normal imaginal disc cells of varying origins and developmental stages will be analyzed biochemically by labeling these macromolecules with radioisotopes and separating them by two-dimensional electrophoresis. Differences in cell surface properties will be examined by measuring the kinetics and specificities of spontaneous reassociation and plant lectin-induced agglutination of dissociated cells. Temporal studies will elucidate the relationship between cell surface properties and accompanying events of cell differentiation and morphogenesis. Finally, the resulting description of normal development will allow the recognition of mutants with cell surface abnormalities. Such mutants will be studied further to determine the involvement of each mutation in cell behavior and morphogenesis, and to infer the normal role of the gene product in development.